Program Director/Principal Investigator: Schryvers, Anthony B. ABSTRACT Neisseria gonorrhoeae, the bacterial pathogen that causes gonorrhea, is now considered an ?Urgent Threat? due to the recent emergence of strains with multi-drug resistance to the antibiotics that are frequently used during treatment. Due to the emergence of these `superbug' strains, we are progressing towards the spread of untreatable gonococcal infections. This situation has added to the urgency for developing a vaccine to prevent these infections, as untreated gonococcal infections can lead to pelvic inflammatory disease, ectopic pregnancy, infertility and invasive infections. Development of a gonococcal vaccine has been challenging due to the remarkable ability of the bacterium to vary its surface components and suppress the development of a protective immune response against reinfection in humans, and due to the lack of appropriate animal models available to study infection and immunity of this pathogen. The primary focus of this proposal is to further develop a protein-based vaccine that targets the constitutively-expressed gonococcal transferrin binding protein B (TbpB), which captures iron from human transferrin. It is an ideal target since the transferrin receptor in N. gonorrhoeae is required for survival on the mucosa and we have shown that it is capable of reducing colonization in a mouse model. We have demonstrated that transferrin-binding defective mutants of TbpB induce a more protective immune response than the wild type proteins, and are currently finalizing the antigenic composition of our TbpB-based vaccine. In this project, we will scale-up and optimize production and purification of our antigens, develop an optimal vaccine formulation and perform all the steps required for implementing Phase I trials in humans. Cross-protection will be evaluated in a lower genital tract colonization model and a model of pelvic inflammatory disease using female transgenic mice expressing human CEACAM receptors and human transferrin, which facilitate gonococcal mucosal attachment and growth, respectively. Together with an industrial sponsor, Vaxiron, Inc., we will develop quality control tools and metrics for assessing vaccine antigen formulations, transfer production of our vaccine formulation to a contract manufacturing organization, complete all the quality, stability and toxicology studies required for regulatory approval to proceed to a future Phase I clinical trial after the culmination of this project.